An article having a rough surface provides many different properties. More of all, to improve some optical properties of the article, roughening surface of an article is one of the useful methods. For example, roughened or textured surface of light-emitting device is helpful to increase light extraction efficiency.
Currently, one of the methods for roughening semiconductor surface includes the steps of coating a photoresist layer on the surface of the semiconductor, using a mask to align and expose a predetermined area of the photoresist layer, curing or degrading the exposed portion, removing a predetermined portion of the photoresist layer, etching the uncover photoresist layer portion of the semiconductor, and removing the remained portion of the photoresist layer. In this method of roughening semiconductor surface, the manufacturing process is complicated and the cost is also high because the equipment for the alignment process is expensive. In addition, the mask needs to be customized for the various dimensions and patterns of the rough surface.
Another method for forming a rough surface on an optoelectronic element is directly etching the surface of the element without using a mask. For example, the etchant of wet etching has different etching rate depending on which crystalline plane of a crystallized material is etched. However, it is difficult to control the surface morphology.
In addition, the light-emitting device can be further connected to other components in order to form a light emitting apparatus. The light-emitting device may be mounted onto a submount with the side of the substrate, or a solder bump or a glue material may be formed between the submount and the nitride-based light-emitting device, therefore a light-emitting apparatus is formed. Besides, the submount further comprises the circuit layout electrically connected to the electrode of the light-emitting device via an electrical conductive structure such as a metal wire.